Aquaculture has been developing remarkably in recent years. In accordance therewith, deterioration in the freshness of such rich-haul fishes as sardine and mackerel, which are used as feed for cultured fishes, causes a serious problem in that cultured fishes suffer from hepatic disorders due to the high peroxylipid content in the deteriorated fish feed.
It is feared that the hepatic disorders will become aggravated and chronic under the stress of farming conditions. It is known that glutathione (.gamma.-L-glutamyl-L-cysteinylglycine) is useful for the prevention and treatment of such hepatic disorders (Japanese Published Unexamined Patent Application No. 156349/1985).
Because glutathione, i.e., a thiol compound, is an unstable compound, it has an unsatisfactory effect when its use method is improper.
Even if it is properly used, glutathione is not sufficiently effective in the case of serious hepatic disorders. Under these circumstances, there has been a demand for the development of a compound which is stable and achieves satisfactory effects on serious hepatic disorders.